drivers: qcom: system_pm: add system_pm device bindings

Add system_pm mailbox client to send sleep and active votes when
entering system low power modes.

Change-Id: Ic76cd74ce3718af76eb88c8c880a199072019123
Signed-off-by: Lina Iyer <ilina@codeaurora.org>
diff --git a/arch/arm64/boot/dts/qcom/msmskunk.dtsi b/arch/arm64/boot/dts/qcom/msmskunk.dtsi
index f600fd9..11e63e6 100644
--- a/arch/arm64/boot/dts/qcom/msmskunk.dtsi
+++ b/arch/arm64/boot/dts/qcom/msmskunk.dtsi
@@ -635,6 +635,11 @@
 				<ACTIVE_TCS  0>,
 				<CONTROL_TCS 1>;
 	};
+
+	system_pm {
+		compatible = "qcom,system-pm";
+		mboxes = <&apps_rsc 0>;
+	};
 };
 
 &pcie_0_gdsc {